1. Field of the Invention
This invention relates generally to semiconductor wafer processing systems, apparatuses, and methods. In particular, the present invention relates to a structure with vertically-stacked process chambers which minimize the footprint while maximizing throughput of a semiconductor wafer processing system. For example, the present invention may be used to translate wafers within a near-atmospheric chemical vapor deposition (CVD) system, a rapid thermal oxidation system, or other types of wafer processing systems. The invention also particularly relates to a wafer transfer apparatus and method that moves semiconductor wafers between a loadlock chamber and a process chamber using a unitary transfer arm which pivots about a single rotational axis.
2. Description of Related Art
Conventionally, wafer transfer between loadlock chambers and process chambers is performed by complex apparatus. The complexity of the machinery has resulted in high cost of the apparatus, slow wafer processing and a short mean time between failures.
One example of a conventional wafer processing system is U.S. Pat. No. 4,934,315 to Linnebach et al. for “System for Producing Semiconductor Layer Structures By Way of Epitaxial Growth”. This multiple reactor chamber system accepts wafers for processing, where the wafers are loaded into respective holders in an atmospheric handler. The holders and wafers are stacked in a load chamber where each holder, carrying its respective wafer, is subsequently transferred along a linear path through the multiple reactor chambers. The reactor chambers are horizontally aligned along the linear path.
U.S. Pat. No. 4,822,756 to Hirayama for “Reaction Furnace and Method of Operating the Same” discloses a reaction furnace including a wafer support boat which rolls from an elevator capsule through a loading chamber and into a treatment chamber. Although the loading chambers and the treatment chambers appear to be stacked in a vertical direction, the pressure gas system and vacuum system are horizontally disposed from the treatment chambers and thus disadvantageously increases the footprint of the reaction furnace.
U.S. Pat. No. 4,423,701 to Nath et al. for “Glow Discharge Deposition Apparatus Including a Non-Horizontally Disposed Cathode” discloses a multiple chamber glow discharge deposition apparatus having deposition chambers which vertically orient the wafers or substrates for processing. The deposition chambers are shown to be horizontally oriented with respect to one another. A rotatable arm expels the substrates from the chamber such that the arm pushes the substrates in one direction along channeled guides.
U.S. Pat. No. 4,816,098 to Davis et al. for “Apparatus for Transferring Workpieces” discloses a system in which wafers are loaded onto the system in a vacuum wafer carrier which is held under vacuum to reduce contamination of the wafers. The wafers are transferred into a cluster tool having multiple process modules via a vacuum loadlock and a 2-axis robot arm which only has the capability of transporting a single wafer at a time.
U.S. Pat. No. 5,664,254 to Ohkura et al. for “Substrate Processing Apparatus and Substrate Processing Method” discloses a stacking arrangement for a plurality of process units. Although the process units may be vertically stacked, only one main handler is provided for transferring substrates to each of the process units, whereby the throughput of each process unit cannot be maximized. The patent also discloses a plurality of holding arms arranged in a 3-stage structure for transferring a substrate or wafer. The holding arms are mounted on the main handler and are actuated by a complex arrangement including a vertical drive shaft and motor in combination with a horizontally oriented convey base having a drive motor and belt to actuate each holding arm.
U.S. Pat. No. 5,058,526 to Matsushita et al. for “Vertical Load Lock Reduced-Pressure Type Chemical Vapor Deposition Apparatus” discloses a loading/unloading chamber which is similar to a loadlock chamber found in a conventional cluster tool. A cooler including refrigerant-circulating tubes located in an unloading part of a loading/unloading chamber cools the treated wafers.
U.S. Pat. No. 5,664,925 to Muka et al. for “Batchloader for Load Lock” discloses a conventional single-wafer scissor-type transfer arm. Similar conventional single-wafer scissor-type transfer arms are disclosed by U.S. Pat. No. 5,613,821 to Muka et al. for “Cluster Tool Batchloader of Substrate Carrier” and U.S. Pat. No. 5,607,276 to Muka et al. for “Batchloader for Substrate Carrier on Load Lock”.
U.S. Pat. No. 5,778,968 to Hendrickson et al. for “Method for Heating or Cooling Wafers” discloses a method for heating or cooling a substrate enclosed vacuum chamber using gas having an adjustable pressure above the wafer. Similarly, U.S. Pat. No. 5,588,827 to Muka for “Passive Gas Substrate Thermal Conditioning Apparatus and Method” discloses a heat transfer plate, located in a thermal conditioning chamber, which is either heated or cooled to change the temperature of a substrate.